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Monday, 23 April 2012

Climate Change: What Are Our Chances?

Industrialised countries have decided that, in order to avoid the most severe impacts of climate change, warming of more than 2oC (above pre-industrialised levels) should be avoided. Any higher than this and the possibility of hitting tipping points becomes much higher. For example, large quantities of potent greenhouse gases locked in frozen soil could be released, which increases warming, which increases the amount released from the frozen soil and so on. Using a few simple numbers we can work out how likely it is that we will limit global warming to this level.

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The author would like people to know that this is in no way peer reviewed, information is from the media and wider public domain and, as such, should not be judged as scientific fact. This article is a reflection of personal opinions, not necessarily the author's, and does not reflect the views or opinions of any the author's commercial or academic associates.

Our home. Its relatively stable climate has allowed humanity to prosper but how long will this continue?

Firstly, it’s worth mentioning that we’ve already released enough greenhouse gasses (GHGs) to warm the planet by 1.3oC , so we don’t have much room to manoeuvre, and we’ve been accelerating the amount of GHGs we’ve been releasing to the atmosphere [1,2]. There appears to be some sort of paradox developing, as the more we talk about global warming and how bad it will be, the more GHGs we release.

The IPCC suggests that if we are to have roughly a 50% chance of not surpassing a warming of 2oC we can’t emit more than about 500 billion tonnes of carbon equivalent (500 Gigatonnes C-eq) from the year 2000 to 2100 [3]. Carbon equivalence takes into account the fact that each of the GHGs have different strengths depending on how well they trap heat compared to the reference GHG, which is carbon dioxide (CO2).*

Now so far, over the past decade or so, we’ve already emitted around 100 GtC equivalent so we have 400 GtC-eq left [2]. Another problem is that unless we become masters of geoengineering (more on this later) humanity is unlikely to ever emit zero GHGs. The reason for this is thanks to nitrogen fertiliser.

Fritz Haber, Nobel Prize winning chemist. Helped feed about half of today's human population byinventing cheap industrial sources of reactivenitrogen. (He also played a crucial part in chemicalwarfare during WWI.)

Around 100 years ago scientists realised that there wasn’t enough nitrogen being fed to the soil by natural processes for plants to thrive and this was worrying as the population was increasing. Fortunately, a German chemist by the name of Fritz Haber, worked out an efficient way of taking nitrogen from the air and creating the necessary form for fertiliser production [4]. This was brilliant but unfortunately has some downsides. Introducing nitrogen to the soil inevitably leads to the formation, thanks to some pesky microorganisms, of nitrous oxide (N2O) - a GHG 300 times more potent by mass than CO2 [5]. Therefore, even if a population of 9 billion were to suddenly become vegetarians (vegetarians produce fewer GHGs [6]), we’d likely emit at least 2 GtC-eq GHGs per year [2]. This seems unlikely to happen. In fact, as people are becoming richer, they’re eating more meat [7].

So let’s say, for the sake of argument, that by 2050 all humans are vegetarian and we adopt very efficient means for producing food. Implying, that we’ll produce 2 GtC per year x 50 years = 100 GtC-eq, for the remainder of the 21st century. If we were to adopt a zero carbon global economy then that’s all we’d release. Meaning that from now until 2050 we have around 300 GtC remaining to play with.

This isn’t as much as it sounds, especially given the assumption I’ve just made. To put this into context, if we were to burn all of the recoverable oil and gas, that would probably emit around 230 – 410 GtC. Crucially, in that assumption we don’t emit a single carbon atom from any coal [8]. Now let’s look at what’s going on today. We get, globally, 27% of our primary energy from coal and we’ve now recently become better at burning the once unrecoverable stuff (oil sands and shale gas). We’re also burning ever more coal [9, 10, 11]. Therefore I leave it to you to decide whether we’ll limit our emissions to stop 2oC warming.

Oil sands: A potential game changer for the fossil fuel industry and maybe game over for a stable climate.

Now, some of you may be thinking “Ok, so it seems very unlikely we’ll reduce our emissions to limit warming to 2oC . But hey, Fritz Haber came up with a process to stop mass starvation and his process now feeds 50% of the global population. I’m sure science will save us.” This magical technology you’d be referring to is geoengineering.

Geoengineering is split into two processes: Carbon Dioxide Removal (CDR) and Solar Radiation Management (SRM) methods. One consists of building large CO2 vacuum cleaners that suck this GHG from the air and hiding it somewhere for a very long time. The other tries to reflect some of the sunlight to cool the planet [12].

The problem with most CDR systems is the large amounts of energy they consume. The concentration of CO2 in the atmosphere is 0.04% and to concentrate that and then compress, pump and bury it takes lots of energy, potentially something equivalent to the global electricity production just to operate these vacuum cleaners [12, 13]!

The problem with SRM systems is that we’d be treating the symptoms not the disease. In other words, we’re trying to cool down the planets temperature but not actually tackle what’s causing it (the high concentration of GHGs in the atmosphere). So if this system were to fail, which it might do, then we’d be in a real pickle as all those GHGs would then rather quickly warm up the planet, especially if we just carried on emitting more GHGs in the meantime. There are also other problems with not addressing the high CO2 concentration. Namely, that the oceans will start absorbing the CO2 and become more acidic (this is already happening) which could seriously endanger marine life [12, 14].

To summarise, the climate is being treated like an alcoholic’s liver. The owner of said liver, us, is going out every other night and getting hammered. We’ve been told that this isn’t good for us and we should stop but hey, liquor/fossil fuels are fun. The alcoholic may be thinking that in the future they’ll be able to grow him a new liver in a lab (which maybe they will and maybe they won’t), although there are risks associated with any operation. And really we all know a better idea would be not to dump alcohol into the body or in humanity’s case, GHGs into the atmosphere, in the first place.

Finally, I’d like to get to the real point of this article; that the 2oC limit is pretty arbitrary. It’s not like 1.9oC warming is dandy whereas 2.1oC is Four Horsemen stuff. The real issue is that as we go further above 2oC , more people start to suffer from the adverse impacts of climate change – especially future generations [15]. Make no mistake, 2oC would be bad news for some of the poorest on the planet and rather unfairly they haven’t really contributed to the problem. However, humanity adapts, it’s what allowed us to wander out of the savannah and become the dominant species on the planet. But as we emit more GHGs to the atmosphere, the more we’ll test humanity's limits. Consequently, we need to develop, and more importantly use, low carbon technology that will limit GHG concentrations. Also it’s important to note that the fewer technologies we have on the table, whether it’s different kinds of nuclear reactors or different types of renewables or even carbon capture and storage devices, the more likely we are to fail. And if we were to fail, well, the further we go above 2oC the more likely we are to hit unstable states whereby warming of 4oC or even 5+oC may be awaiting us [16]. To put that into context, the difference between now and the last ice age is only 5oC [17].

*Note that a CO2 molecule is 3.7 times heavier than a carbon atom so to convert from carbon to CO2-eq multiply by 3.7.

This 490 GtC equivalent (I rounded to 500 GtC-eq) would give an atmospheric GHG concentration of around 450 ppm CO2-eq and this will give roughly a 50% chance (http://www.ipcc.ch/publications_and_data/ar4/wg2/en/ch19s19-4-2-2.html) of not exceeding 2oC warming. We should be asking ourselves that if politicians (http://news.bbc.co.uk/1/hi/sci/tech/8414626.stm) have decided that we want to limit global warming to 2oC, then maybe a GHG concentration of 450 ppm CO2-eq is too high, as essentially we’re giving ourselves the same odds of hitting this target as flipping a coin! Therefore, if the 450 ppm target is quite a big gamble why aren’t we going any lower. The reason is that anything below this is even less likely to be achieved. We might as well set a target that there’s still a very slim chance of hitting. The Stern Review proposed an atmospheric concentration 550 ppm CO2 equivalent (even though this gives only about a 15% of not exceeding 2C). The reason, if you were wondering, for the 550 ppm target is that for us to achieve a 450 ppm CO2-eq there would likely be a big impact on global GDP in the short term. However, Nicholas Stern has now changed his mind on this 550 ppm limit. (http://www.nature.com/climate/2009/0905/full/climate.2009.34.html)

(You'll notice that every number above is plagued with uncertainty. This is because climate modelling is difficult. However, uncertainty shouldn't be used as an argument for slower reductions in GHG emissions. If anything, it's a good reason for larger reductions due to the possible size of these negative impacts.)

The importance of the Haber process (named after Prof Fritz Haber) cannot be understated. If it weren’t for this amazing feat of chemical engineering maybe up to half the population would not be alive today. It has been described as "creating bread from air." However, by allowing the global population to expand the Haber process can also be considered as playing another important part in increasing our global emissions i.e. as there are more people knocking around and people inevitably produce GHGs due to their living requirements, it has increased GHGs further. I would like to state that whilst there are people who think global population is the elephant in the room and we need to dramatically reduce our number, I completely disagree. For one, I can't think of a civilised way of doing this that would seriously help us reduce our GHG emissions. Secondly, the real problem is that most of our energy comes from highly polluting sources. There are certainly civilised ways we can decelerate forecasted population growth (http://www.youtube.com/watch?v=fTznEIZRkLg) but the idea that by cutting our population we'll save ourselves from severe climate change is clap trap. If you have 1 billion people with a carbon footprint of the average Qatari then we'd end up releasing more CO2 than we do now! A planet with 9 billion people having their needs met is possible without having severe climate change.

[5] Agriculture. In Climate Change 2007: Mitigation. Contribution of Working Group III to the Fourth Assessment Report of the

Vegetarians have a lower carbon footprint as they consume less meat and meat is an inefficient form of calories – it takes 7 kg of feed grain to produce 1 kg of beef – plus there’s the problem with methane from cattle (methane is around 20 times more potent than CO2). See page 101.

Interestingly we can look at land use efficiency too, as not only do greater numbers of crops need to be grown but we also need to give the animals some space to live, which increases the land requirement. The land requirement for cattle is around thirty times that of cereals to produce the same calorie content.

[8] This requires some back-of-the-envelope work:

Now depending on whom you talk to, there may be somewhere between 1.2 – 2.9 trillion barrels of recoverable oil that’s ready for the taking and maybe around 190 trillion cubic metres of natural gas (see here http://www.bp.com/sectiongenericarticle800.do?categoryId=9037178&contentId=7068624 and here http://www.amazon.co.uk/Oil-Panic-Global-Crisis-Predictions/dp/1405195487). Using the fact that a cubic metre of gas produces 0.5 kg of carbon and 1 barrel gives us 110 kg of carbon we get around 230 – 410 GtC. The uncertainty on how much recoverable oil and gas there may be is huge. Canada alone could have potentially 1 trillion-plus barrels locked in its oil sands. I'm not going to mention peak oil, the point at which maximum oil extraction rate is hit, which would slow down how much we can get out of the ground. The key point here is that there is lots of oil and potentially staggering amounts of nearly oil (oil that with a little bit of chemical wizardry we can put into machines). If we can bring this stuff online quickly enough to meet demand then we're going to give the planet a serious fever. And remember, I haven't even discussed how much coal could be out there. Plus our current farming habits are probably producing 3 - 4 GtC equivalent GHGs every year and there are currently around 1 billion malnourished people on the planet [6]. Never mind industry emissions, which produce around 20% of manmade GHGs (http://withbotheyesopen.com/read.php?c=5) (this isn't just emissions from the fossil fuel energy - a large proportion is from the inevitable GHG releasing chemical reactions that take place when producing aluminium, cement, iron, steel, fertiliser, etc...). The point being that we have many sources of GHGs not just oil and gas.

Whilst about 27% of global primary energy is supplied from burning coal, 43% of emissions due to generating this energy are from coal, more than any other source. This is simply because coal emits more CO2 per unit of energy compared to other fossil fuels.

For those interested in geoengineering, this report by the royal society is definitely worth a read. There are many different types of CDR and SRM methods and my generalistic statement isn't enough to describe them properly. The conclusions are that certain types of SRM allow very rapid reductions in global temperatures, although in likely the most affordable/rapid option (dumping loads of particles into the atmosphere) there are big unknowns into how the atmospheric chemistry and physics would behave. There is also the risk that the small particles could group together and as they get bigger their ability to reflect sunlight becomes weaker or they could simply fall back to earth. Sucking it from the air is probably the best option (well, the best option would be not to put it there in the first place) although we'd need to find somewhere safe to store the CO2. If we can bring carbon capture and storage (http://www.guardian.co.uk/environment/interactive/2008/jun/12/carbon.capture) online and in large scale, that would at least increase our confidence in how well we can store the stuff. In the future, if we keep accelerating our emissions of other GHGs we may need to come up with other removal systems for these.

We could also grow large solar powered vacuum cleaners, commonly named trees, and then burn and bury the CO2. This is definitely possible but for it to make a large dent in global CO2 emissions they’d likely start competing with land and water for food production.

Oh and if you’re thinking that the oceans will save us by absorbing all the CO2 quickly you’d sadly be wrong. For it to significantly reduce the CO2 concentration in the atmosphere it’ll take the oceans thousands of years [15].

The Stern Review states that a 5°C global average temperature change "would take humans into unknown territory. An illustration of the scale of such an increase is that we are now only around 5°C warmer than in the last ice age."